The first time my heart beat alarmingly hard and fast, I was 11 years old. I was in the middle of a dance class but knew something was wrong, so I left class and told my parents what was happening. They helped calm me down, and soon my heartbeat returned to normal.
After that first incident, the episodes kept coming, usually catching me unaware. They didn’t seem to be triggered by anything in particular: All of a sudden, my heart would start racing, making me feel tired and weak. Sometimes an episode lasted only minutes, and I could go back to what I was doing with little interruption. Other times, it lasted long enough to drain my energy, and all I wanted to do was sleep. Once, my heart raced for more than three hours.
My pediatrician referred me to a heart specialist at Seattle Children’s Hospital, who determined I had supraventricular tachycardia (SVT). SVT is an abnormal heart rhythm (also called an arrhythmia) that originates in the heart’s upper chambers, or atria, where electrical signals are received.
Normally, the sinoatrial node, a pacemaker in the right atrium, sets the heart’s rhythm. But in SVT, rapid abnormal electrical signals in the atrium overtake the sinoatrial node’s rhythm and cause the heart to race. The heart’s rapidity can mean it doesn’t pump blood effectively, causing dizziness and shortness of breath.
When the heart short-circuits
If you’ve never heard of SVT, you aren’t alone. I never had until I got it, and most people are unfamiliar with the term when I tell them about it. Yet, SVT isn’t that rare. About two in every 1,000 people have it, which translates to nearly 90,000 new cases each year. That’s more common than congenital heart defects, which are present in about 40,000 births annually.
Unlike ventricular tachycardia, which originates in the lower part of the heart (the ventricles) and leads to sudden cardiac arrest, SVT is not usually dangerous on its own. It can occur in someone who has a preexisting heart condition, but it can also occur in someone whose heart is structurally normal.
Treating patients with SVT is an everyday occurrence for Nazem Akoum, M.D., a cardiologist and director of the atrial fibrillation program at the UW Medicine Regional Heart Center.